The 1100 had a nasty vibration between 4000 and 4500 rpm. After trying out several other things it finally turned out to be a crack in the right exhaust pipe just beneath the heat shield. Once I took the heat shield off the crack was far more obvious. I removed the exhaust to have it patched and the pipe actually split in half. There was also a weld on the left pipe that had failed. I had both areas welded up and everything is good as new. No more vibration. The bike is running smooth again.